To address widespread concerns about cancer risks from magnetic fields in the home, investigators from NCI and from the Children's Cancer Group are conducting a case-control study of childhood acute lymphoblastic leukemia. Data collection has been completed and includes information on 638 cases and 620 controls under age 15. Measurements of magnetic fields in the child's bedroom, the family room, the kitchen, and the area immediately outside the front door will be used to assess exposure. Another exposure assessment will be based on the distance and configuration of power lines near the home, and the exposure of the mother during pregnancy will be similarly evaluated. We have reported on the methodology for exposure assessment, including a special calibration study based on personal dosimetry, and we are analyzing the data on cancer risk. We have also launched a case-control study of adult brain cancer (glioma, meningioma, and acoustic neuroma) to investigate cellular telephone use and other possible risk factors. In collaboration with investigators in Boston, Phoenix, and Pittsburgh, we will enroll approximately 700 cases and 700 controls who are hospitalized with a variety of nonmalignant conditions. Approximately half the required numbers of cases and controls have been enrolled and interviewed, and data collection is expected to be completed in 1998. We are studying two cohorts of shipboard radar operators and maintenance workers who served in the U.S. Navy during the Korean War. We are determining the risk of cancer mortality for groups exposed to various levels of microwave and radio frequency radiation.